David Cameron once demanded a "big bazooka" to solve the euro crisis. In the event, big enough blasts were fired to quieten market monsters, but never to finally silence them; lingering fear still haunts a continent. Japan's very different crisis, however, has lingered for longer, for so long that it ought instead to be called a permanent stasis – since 1990 to be precise. Rock-bottom interest rates, a depressed yen, stimulus and austerity have all been tried in various combinations. The economy has disregarded the lot, remorselessly rolling from lukewarm recovery to fresh recession and back. But now Tokyo is letting rip with a new bazooka that is big by any standards.

In accordance with wishes of Prime Minister Shinzo Abe, the supposedly independent Bank of Japan has explained how it will pursue inflation. In an economy where falling prices have often been the norm, the stock of money will be doubled in 21 months, and the newly minted currency will be used in novel ways; specifically, to purchase government debt from – in the jargon – across the yield curve. Both elements represent a radical departure in their own right. Nothing on this scale has been tried before, not even when the world's central bankers worked in panicked concert in 2008. And the whole world must now pray that the plan comes off in what remains its second-biggest mature economy: a recovered Japan really could boost a stagnant planet.

But is that likely? It can't be ruled out. This was not, as some said, a crude invitation to competitive devaluation: Tokyo is less concerned with the price of yen than with prices in Japanese shops. Even if trading partners cheapen their currencies in reply, it may be no bad thing. During the 1930s, beggar-my-neighbour policies cancelled out in terms of export sales, but the cheapening of currencies nonetheless helped ease debt deflation.

Big bazookas are hard to control, and those wielding the weapon could shoot themselves in the foot. Japan needs to persuade its people that prices will rise, but if expectations of excessive inflation are stoked, investors could take fright, causing borrowing costs to rise. It is a risk, though not one that aggressive monetary expansion in the US or Britain has yet seen realised; besides, risks simply have to be run if the alternative is permanent stagnation.

The deepest doubts arise from Japanese demographics: the typical citizen is four years older even than in ageing Britain. The idea of cheap money is to persuade people to open their wallets, and spend their way to recovery, but in this sort of senior society, fear of inflation eating up pensions could convince people they need to save more and spend less. Let us hope not. Where Japan led, the world has followed since 2008. Fingers crossed that it can now lead the way to a solution.